Static Shock and The Zeta Project are also considered to be in continuity with the DCAU. I'm not sure how Bruce Timm was involved in these shows (if at all), but The Zeta Project was a spinoff of Batman Beyond and Static Shock had crossovers with almost all the other shows (except for The Zeta Project).

Also, FWIW, it's Timmverse, named for Bruce Timm, with two "m"s. that should help if you run searches.

But yeah, I'd say the essentials are Batman: The Animated Series (started it all) then Batman: Mask of the Phantasm, then Superman: TAS, then Batman Beyond, then both Justice League shows. Everything else can be picked up on after.